Airflow is generated incident to the rotation of data storage disks of a disk file. The characteristics of this airflow have been analyzed and reported by E. Lennemann in the IBM Journal of Research and Development, November 1974, pages 480-488. The amount of airflow is known to be a function of disk diameter and angular velocity. The airflow force is greatest adjacent the surface of the rotating disk and falls off rapidly as one moves away from the disk surface. It is also known that multiple commonly mounted, spaced apart rotating disks generate a significantly greater useful airflow than is generated by a single rotating disk. This is because the air between any pair of the disks is effectively trapped, and moves with a velocity comparable to that of the rotating disks themselves.
The assignee of the present invention has pioneered the development and use of a disk drive actuator lock mechanism which employs useful airflow generated by disk rotation to overcome a spring bias force and thereupon release an actuator latch and the actuator when the disks have reached an angular velocity at which the transducer sliders "fly" upon an air bearing cushion. The aerodynamically released actuator latch is described in commonly assigned U.S. Pat. No. 4,538,193 to Dimmick et al., entitled "Aerodynamically Released Safety Latch for Data Transducer Assembly in Rotating Rigid Disk Data Storage Device"; commonly assigned U.S. Pat. No. 4,692,829 to Campbell, entitled "Magnetically Biased Aerodynamically Released Integral Safety Latch for Rigid Disk Drive"; and commonly assigned U.S. Pat. No. 4,647,997 to Westwood, entitled "Aerodynamic Latch for Disk File Actuator". The disclosures of these patents are incorporated herein by reference.
Recognizing the limitations and drawbacks attending limited airflow of a small diameter (3.5") single data storage disk, the latter referenced inventor Westwood innovated the provision of an airflow generator "dummy" disk which was commonly mounted to a spindle hub in spaced-apart relation with the data storage disk. During rotation of the spindle hub, sufficient useful airflow is generated between the disks to deflect the pivoted, spring biased air vane disposed therebetween. One drawback of Westwood's airflow generator disk solution was the added cost associated with the airflow disk, an added cost amounting to about a dollar in mass production. The rigid disk drive business is now so competitive, especially at the lower capacity/price points, that unessential added costs, such as the incremental costs associated with the airflow generator disk, are no longer acceptable. Another disadvantage of the airflow disk solution was that, as the airflow disk was a thin, flat structural part with relatively large area, it proved difficult to mold from low-cost thermoplastic material without warpage or distortion. Yet another disadvantage of the airflow disk solution was that the additional vertical space the disk occupied added to the overall height (thickness) dimension of the disk drive head and disk assembly, by as much as 2-3 millimeters, or more. Since rigid disk drives are increasingly used in portable and lap top computers, it is desirable to make the disk drives as thin, compact and light in weight as possible.
IBM has proposed a disk drive product, Model WDA-L42/WDS-L42, employing a single data storage disk for generating airflow for operating an aerodynamically released actuator latch. The IBM approach is not without its drawbacks. When the amount of available useful airflow is reduced from a two-disk airflow arrangement to a single-disk airflow arrangement, there must be a corresponding reduction in spring bias force applied to the aerodynamic latch to bias it to a latched position for holding the actuator in a head parking position whenever the disk is not rotating. When the spring bias force is reduced so as to be overcome by a reduced force generated by reduced useful airflow, the latching mechanism becomes sluggish and less reliable in releasing the actuator latch in intended fashion.
It is known to enhance the level of air flowing as a consequence of rotation of a fixed data storage disk. One known reason for increasing airflow is to provide an adequate air cushion or bearing for the data transducer as it flies by the rotating disk. Another reason is to provide a cooling fluid for cooling an in-hub DC brushless spindle motor. An example of a disk drive employing a turbopump technique to enhance air flow is given in U.S. Pat. No. 4,101,945 to Butsch entitled: "rive Spindle Assembly for Disc File". In that approach, the turbopump is formed as an integral part of the disk hub, and not as a part of the disk clamp which secures the disk to the hub. The use of the increased airflow was not for the purpose of releasing an actuator latch.
Thus, a hitherto unsolved need has arisen for a method and apparatus for enhancing the level of airflow within a single disk data storage device for operating an aerodynamically released actuator latch mechanism.